A series of steps for fabricating a semiconductor device or a flat panel display includes a step of processing a process object, such as a semiconductor wafer or a substrate for a liquid crystal display, with various process gases. In a case where a photoresist coated on a semiconductor wafer is to be removed, there is performed a process step that supplies a process gas comprising ozone and water vapor to the semiconductor wafer under high temperature and high pressure, thereby to render the photoresist on the semiconductor wafer water-soluble.
In a processing apparatus employed to perform the above process step, plural gas flow lines is provided to supply a process gas into a process chamber and to discharge the process gas from the process chamber. On a gas flow line through which a process gas flows, a diaphragm valve is provided for opening or shutting-off the gas flow line, or for controlling the internal pressure of the process chamber (See JP2004-2733553A, for example).
It is observed that a diaphragm valve element is electrically charged due to friction between the process gas and the diaphragm valve element when the process gas flows through the diaphragm valve. In a case where the process gas is a corrosive gas such as ozone, it is preferable that the material of the diaphragm valve element be a resin having excellent corrosion and chemical resistance such as a fluorine resin. However, a diaphragm valve element formed of a resin is likely to be electrically charged due to its low conductivity.
If the diaphragm valve element is electrically charged, it is possible that spark discharge occurs, and resultantly the diaphragm valve element is damaged so that pin holes are formed therein. Thus, the diaphragm valve element no longer functions properly, and it is possible that the processing of the process object can not be carried out properly.